dc and ac characterizations of WO3 sensors under ethanol vapors

Room temperature ammonia sensing properties of W18O49 nanowires

“…The abnormal behavior of the response of the WONWs to ammonia can be explained if the diameter of the WONWs (less than 5 nm) is less than the Debye-length at room temperature when the bulk donor density of the WONWs is in a proper range. By adopting the typical values of √ ε = 2.29 and N D = 4-6 × 10 15 cm 3 for typically sputtered tungsten oxide thin films [21,22], the Debye-length at room temperature is calculated to be about 45-50 nm. We cannot use this value directly as the Debye-length for the WONWs since the donor density of the WONWs is affected by the oxygen vacancies in the nanowires.…”

Semiconductor Gas Sensors: Dry Synthesis and Application

“…[187,204] Annealing temperatures for tungsten oxides are typically in the range of 350-600 8C. [179,184,188,205,206] For heterogeneous nucleation processes (Figure 7), crystalline films are rarely obtained directly during deposition, unless the substrates are heated as described for PLD and SP. [123,141] However, in processes where the particle-and filmformation zones are decoupled in the reactor (gas-phase nucleation: Figure 7), crystalline films can form directly and post-synthesis annealing is not required.…”

Bias dependent sensitivity in metal-oxide gas sensors

“…In typical operating temperatures of resistive metal-oxide gas sensors, 300-400 • C, oxygen is chemisorbed dissociatively and the atomic oxygen O − ion is the dominant oxygen species on the surface [1,3,5,[13][14][15]. In this case the oxygen chemisorption reaction can be written as [6,7] 1 2 O 2 gas + S O ads (18) where S denotes an adsorption site.…”